1) Field of the Invention
The present invention relates to manometers, and more particularly, to a durable, economical, high volume, high precision manometer which can easily be operated and taught in a classroom setting, is leaks resistant, disposable at low cost if employed for handling radio active solid substrates, and which allows for the manometer to be reset without exposing the interior of the apparatus to external ambient air.
2) Description of Related Art
The prior art is replete with various devices for measuring pressure differentials on a liquid medium caused by gas exchange. However, the vast majority of these devices that attempt to provide accurate high precision results are extremely expensive to manufacture, fragile, and difficult to operate without leaks, even for experienced lab technicians. Further, digital gas measurement devices do not permit students to see the gas produced in many cases, as it is often detected in solution in a fluid environment. Digital sensors also have the disadvantage of a useful life of 18 to 24 months due to wear of the probe materials, requiring schools to reinvest in the expensive detection device or risk classroom downtime.
The quantitative instruction of students about catalase reactions and respiration in an average classroom or school laboratory setting has been frustrated by the cost of equipment, complexity of the equipment and consequential gleaning of data. Importantly, the matching of substrates to equipment size must be such that a reaction can be set up and data determined within the class time period available. At the present time, the most common means of examination of gas exchange or production reactions would be conducted in what is termed a Warburg apparatus.
The Warburg apparatus is a complex manometer. It employs an expensive flask of small size immersed in a fluid bath of constant temperature. The constant temperature is employed so that comparisons can be made between flasks employing very small volumes of gas expired from tissues, which is measured in microliters. The initial cost of the fluid incubator, agitator set-up, manometer tubes, and fitted glassware for three trial samples is approximately $2000, or more. It has been stated by the American Society of Microbiologists (Manual of Methods for General Bacteriology, pg. 325, section 16.6, Manometry) that manometry is essentially a research matter threatening to become a “lost art” due to an insufficiency of time to teach proficiency with such apparatus as a Warburg manometer.
During set up of a Warburg apparatus, what is know as a flask constant would require determination using mercury or a defined fluid. This is done in a Warburg situation because the amount of gas which could dissolve in the fluid of a Warburg is large in proportion to the space available. The Warburg output values are generally measured in micro-liters. For fast reactions such as the reaction of peroxide with a few grams of tissue or seeds, as would be used in a classroom environment, the Warburg capacity to measure output gas is used up rapidly since tissue gas output from peroxide can be in milliliters per minute rather than micro-liters per minute. The Warburg often requires frequent resetting of the manometer to release excess gas and reset the apparatus for further experimentation. When several manometers are running at once in a Warburg bath under fast reaction conditions, the resetting times for each manometer can become excessive and overly burdensome, particularly in a student circumstance. This also demands the manometers in line be reset to avoid running over their capacity, and ruining the experiments being conducted. The matching of tissue volume and substrate in the Warburg apparatus has become a tedium causing it to be employed mainly as a research tool. Further, leaks caused by the multitude of connections to tubes and flasks in such apparatus have been a major source of frustration in obtaining consistent accurate results in measurement.
For the student experiencing manometry for the first time, the tedium of loading, sealing off leaks, and finding the constants involved in using a Warburg apparatus are overwhelming and take far too long for a single class period. It takes considerable time to get accomplished with the apparatus and the limited volume of the Warburg essentially makes it useless for conducting the type of vigorous reactions that can provide students with useful results in a single class time period.